Florida is a Must Win for Romney

If Mr. Romney loses Florida, he has only one way to victory: through all the other battleground states. He has led most polls there, however, and is the favorite. If Mr. Romney wins Florida, he has 75 paths open to him.

Ohio: Obama's Firewall

Of the three largest battleground states, Mr. Obama has the largest lead in Ohio – partly because of a strong local economy and the auto industry bailout. If he loses here, it's likely he will trail in Florida and North Carolina too. Losing all three leaves him with only 14 ways to win.

Times's Battlegrounds

Nine states are shown above, but The Times rates only seven of them as battlegrounds. If Nevada goes to Mr. Obama and North Carolina goes to Mr. Romney, as The Times’s ratings suggest, the president will have four times as many paths to victory as his opponent.

Edge of Your Seat Possibilities

There are five paths to a tie. In this case, the newly elected House of Representatives would select the president (likely Mr. Romney) and the Senate would select the vice president (possibly Joseph R. Biden Jr.).